It looks like that JavaScript code for the poll was originally written for an older version of BE.

On your page, I see about 4 JS functions for the poll -- beginVote, endVote, showResult and showPoll. Within those functions, in various places, it has lines of code beginning like $('.....'). Those lines of code should be changed so instead
of:

$('....')

It is:

BlogEngine.$('....')

So basically prefix the $ with BlogEngine.

A quick count shows there's about 13 lines that need this adjustment made to it.